v1.9.5.6

v1.9.5.6

New features:

1. back-propagate Ostap::Math::Integrtaor toold versions of PyROOT
2. extend tests
3. add (fictive) Ostap:Math::Thiele::abscissas method
4. add (fictive) Ostap:Math::Thiele::values method
5. add missing __reduce__ for Ostap::Math::Thiele interpolant
6. extend MoreMath.h and math_ve.py
7. add smooth_step polynomial fuctions
8. add explicit functions for derivatives of Bessel functuons
9. make use of explicit derivatives of Bessel fuctions

Backward incompatible:

1. rename some methods for Ostap::Math::Integrator

Bug fixes:

1. Fix typos for Ostap::Math::Integrator